This invention generally concerns gas/liquid separation devices, and is particularly concerned with an oil separator for separating the oil droplets entrained in vent air expelled from the crankcase of an internal combustion engine.
Modern automotive engines including both diesel and gasoline engines are frequently provided with a ventilation system for venting air circulating within the crankcase of the engine. During the operation of the engine, small amounts of hot combustion gases leak past the piston rings and through the oil circulating within the crankcase to create a pressurized mixture of air, exhaust gases and atomized oil. If left unvented, the resulting gas pressure could force the oil in the crankcase to penetrate the seals between the crankshaft and the engine block, not only causing an undesirable loss of engine oil, but also pollution in the form of a constant oil dribble from the vehicle. To mitigate these problems, the crankcases of some internal combustion engines are provided with baffles in front of their vent openings for condensing and at least partially recirculating some of the oil entrained in the vent gases. The vent gases are then discharged through a draft tube mounted on the outside of the crankcase. Such a venting system prevents pressurized oil from breaking through the seals of the crankcase and further reduces some of the oil losses that result from the venting, but unfortunately allows a significant amount of oil to escape out of the draft tube and dribble out of the engine.
Devices for separating the oil from the air stream discharged by crankcase venting systems are known in the art. However, none of these separators thus far has provided an entirely satisfactory solution to the aforementioned problems. The aircraft industry has long used oil separators in connection with prop plane engines that are substantially more efficient than the baffle and draft tube systems previously described. However, the complex structure and consequent high expense of such separators (which cost upwards of several hundred dollars) render them economically impractical for use in car and truck engines. Additionally, none of these prior art separators is capable of satisfactorily recirculating filtered oil back to the oil system of the engine. While one separator is known which attempts to recirculate collected oil back to the crankcase, the applicant has observed that the lack of a positive pressure differential between the drain line of the separator and the air within the crankcase prevents an effective recirculation.
Clearly, what is needed is a practical and economical device that is capable of separating substantially all of the oil droplets entrained in the gases expelled from an engine crankcase ventilation system, and effectively recirculating the separated oil back to the oil supply of the engine. Such an oil separator should be easily retrofittable onto a variety of different makes of internal combustion engines. Ideally, the oil separator should constitute part of a completely "closed" system which, when installed in an engine, eliminates all unwanted emissions of both vaporized and liquid engine oil.